Environmental threats - ameaças ambientais

Acid rain

[pic] Acid rain describes any form of precipitation with high levels of nitric and sulfuric acids. It can also occur in the form of snow, fog, and tiny bits of dry material that settle to Earth. Rotting vegetation and erupting volcanoes release some chemicals that can cause acid rain, but most acid rain falls because of human activities. The biggest culprit is the burning of fossil fuels by coal-burning power plants, factories, and automobiles. When humans burn fossil fuels, sulfur dioxide and nitrogen oxides are released into the atmosphere. These chemical gases react with water, oxygen, and other substances to form mild solutions of sulfuric and nitric acid. When acid rain reaches Earth, it flows across the surface in runoff water, enters water systems, and sinks into the soil. Acid rain has many ecological effects, but none is greater than its impact on lakes, streams, wetlands, and other aquatic environments. This makes waters toxic to crayfish, clams, fish, and other aquatic animals. Acid rain also damages forests, especially those at higher elevations. It robs the soil of essential nutrients and releases aluminum in the soil, which makes it hard for trees to take up water. Trees' leaves and needles are also harmed by acids.

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Deforestation
Deforestation is clearing Earth's forests on a massive scale, often resulting in damage to the quality of the land. Forests still cover about 30 percent of the world’s land area, but swaths the size of Panama are lost each and every year. The world’s rain forests could completely vanish in a hundred years at the current rate of deforestation. Forests are cut down for many reasons, but most of them are related to money or to people’s need to provide for their families.The biggest driver of deforestation is agriculture. Farmers cut forests to provide more room for planting crops or grazing livestock. Often many small farmers will each clear a few acres